I don't know anything about your rifle, but I shoot a sears and roebuck/j.c.higgins 12 ga, and I once asked to find out how old it was, found out that sears stopped sanctioning these arms in the 50's, so I'm betting your gun is around that old. Might write a letter into guns and ammo or contact a gunsmith.

Screw the 10 ring, keep them in the zero!!!